Combustor igniter cup which becomes incandescent from combustion therein



Aug. 18, 1953 T. G. McDouGAL 2,648,951

coMBUs'roR IGNITER CUP WHICH BEcoMEs INcANDEscl-:NT

FROM coMBus'rgoN THEREIN Filed March 31, 1949 :Snventor zzze WLO/QQZ En WM y (ttornegs Patented Aug. 18, 1953 COMBUSTOR IGNITER CUP WHICH BE- COMES INCANDESCENT FROM COM- BUSTION THEREIN Taine G. McDougal, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 31, 1949, Serial No. 84,685

(Cl. (iO-39.82)

3 Claims. l

The present invention relates to ignition systems and particularly to ignition devices especially adaptable to kindle combustible mixtures utilized as propellants in air-borne power plants.

Ignition for such power plants can be provided by an electrical spark discharge between the electrodes of a suitable spark plug or by a glow plug comprising either a resistance wire or a coiled resistance wire mounted within a protecting refractory sheath. Where glow plugs are used the glow plug is generally brought to a temperature condition suitable for the ignition of combustible gases by the passage through the resistance wire of a substantially large quantity of electrical current. Such forms of ignition devices and kindling methods are not particularly satisfactory, however, as they require such components as a generator, battery, transformer or coil and suitable conductors from such components to the igniter unit. Provision of these component accessories involves adding weight to the power plant as well as a multiplicity of units the failure of any one of which may result in operational failure of the system. Furthermore, in many instances such as with expendable missiles the cost of such systems is substantial and the space required for the installation becomes an objectionable consideration.

Accordingly it is the object of the present invention to provide an inexpensive and compact ignition system for the kindling of propellant fuels in air-borne power plants.

It is a further object to provide a glow plug comprising a refractory cup or sheath which is adapted to be brought to a temperature condition for the ignition of combustible fuel mixtures by the combustion therein of relatively small volumes of easily ignitable combustible gases.

These and other objects are attained in accordance with the present invention by providing an ignition device including a fuel igniter housing having a discharge passage leading to an apertured refractory cup secured to the housing to enclose the discharge end of the passage, means in communication with the igniter housing to supply an easily ignitable combustible gas mixture to the interior of the cup and means within the cup for igniting the combustible gas mixture.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention reference may be had to the accompanying drawing in which Figure 1 is a diagrammatic, schematic view with parts broken away and parts in section illustrating a combustion chamber with an ignition device embodying the present invention positioned for ignition of the combustible fuels in the chamber, and Figure 2 is an enlarged View in section of the refractory cup forming the ignition initiating element or glow element of the ignition device.

Referring now to the drawing there is illustrated a combustion chamber comprising an inner compartment or flame tube 2 mounted within a surrounding chamber or air tube 4. A fuel nozzle 6 is positioned in the end of the combustion chamber and is adapted when connected with a source of fuel, not shown, to deliver a conical spray of fuel into the flame tube. The flame tube 2 is provided with a plurality of aperatures 8 which serve to admit air to the ame tube for supporting combustion therein and provide for a continual flow of cooling all around the outer surface of the flame tube.

Positioned in the side wall of the combustion chamber is the igniter housing H) of the ignition device or glow plug. The housing le is provided with a mixing chamber l2 connected by capillary tubes I4 and I6 to receptacles I8 and 20.v The receptacles i8 and 20 are sealed containers or capsules adapted to hold suicient quantities of gases under pressure such as oxygen and hydrogen which when mixed in the proper ratio support combustion. Means are provided for connecting the containers to the capillary tubes through the Valves 22 and 24 which may be of a type including an impaling instrument for penetrating the sealed containers. To obtain a satisfactory ratio of mixed gases in the mixing chamber to support combustion the capillary tubes are selected with a bore adapted to conduct the gases from the containers at a suitable rate of flow to provide the desired combustion ratio in the mixing chamber I2. This may also be accomplished by providing valves such as 22 and E4 with porous metal inserts therein which restrict ilovv'of the gases from the containers to rates adapted to provide a compustible mixture in the mixing chamber.

Attached to the end of the housing l@ is a refractory metal cup 26 of material such as platinum which encloses the discharge passage oriiice of the housing l0. The cup 26, when heated by the burning of the combustible gases therein, is eiective to ignite the main fuel and air introduced into theflame tube through nozzle 6 l and apertures 8. In the housing l0 communication is established between the mixing chamber I2 and the interior of the cup 26 by the discharge passage 28. The cup is provided with a plurality of apertures 30 which permit the burned gases within the cup to escape to the flame tube 2. The apertures are located in the cup walls preferably on the downstream side to insure against extinguishing combustion within the cup due to air currents in the name tube.Y

Within the cup 26 there is positioned a coiled filament 3'2 of wire having a suitable resistance to become incandescent upon the passage therethrough of an electrical current such as that available in a small dry cell type battery. The coil 32 is grounded at one end to the cup and connected at the other end to a switch 33 mounted externally of the combustion chamber by a conductor 34. As

flow of gases under pressure from the containers I8 and 20 to the mixing chamber i2. As has been hereinbefore described, porous metal inserts in the valves or capillary tubes with predetermined bore sizes are provided to permit ow of the gases at rates which will form a combustible mixture in the mixing chamber I2. The mixed gas is forced under pressure through discharge passage 28 into the cup 26 where it is ignited by exposure to the incandescent filament 32 brought to incandescence by closure of switch 33. With combustion taking place in cup 26, the cup is brought to a condition of incandescence suitable for the ignition of the combustible main fuel mixture in the flame tube 2. To insure that the glowing cup will be in a fuel zone supporting combustion in flame tube 2, the cup is located so that its ends extend into the conical spray area of nozzle 6; this being the area in which the air entering flame tube 2 through apertures B joins the stream of fuel from nozzle 6 to form a combustible mixture.

A system such as that hereinabove described will provide a compact, inexpensive and efflcient ignition system for air-borne power plants and will find particularly useful application in connection with the use of power plants employed in expendable missiles. While I have shown a particular embodiment of my invention it will be understood, of course, that I do not wish to be limited thereto since other modifications may be made, and I therefore contemplate by the appended -claims to cover any such modifications as fall within the true spirit and scope of the invention.

What I claim and desire to secure by Letters Patent of the United States is:

1. In a fuel ignition system, a plurality of receptacles containing gases under compression, said gases being adapted for mixing to provide a combustible mixture, an igniter having a housing defining a mixing chamber therein and a discharge passage communicating with said mixing chamber, means connecting said receptacles with said mixing chamber for conducting gases from said receptacles to said mixing chamber,

The other side of the switch 33 is L.

said means being adapted to restrict flow of said gases from said receptacles to said mixing chamber at a ratio to provide a combustible mixture in said mixing chamber, a refractory metal cup attached to the said housing to surround said discharge passage outlet, said cup having a plurality of outlet apertures therein and being adapted to become incandescent by the -combustion of gases therein, a resistance filament positioned within said cup with one end grounded thereto, and a source of current connected to the other end of said lament for providing current to cause said filament to glow and ignite said combustible mixture in said cup.

2. In combination a main combustion chamber, a source of primary -combustible fuel for causing high velocity flow of fuel into said chamber, an igniter extending into said combustion chamber, said igniter comprising a housing having a mixing chamber therein and a discharge passageway communicating therewith, means for supplying combustible gas to said mixing chamber to be discharged through said passageway, a refractory hollow member having openings therein and capable of being heated to luminescence, said member being mounted on the housing over the end of the discharge passage in the main combustion chamber and being free of openings in the up-Stream surface thereof, a resistance filament mounted within said chamber and protected by the continuous portions of said member, and a small source of electrical power connected to said filament for igniting said combustible gas as it flows from the mixing chamber through the discharge passageway, the combustion of such combustible gas being effective to heat the refractory member to luminescence.

3. In combination a main combustion chamber, a source of primary combustible fuel for causing high velocity flow of fuel into said chamber, an igniter extending into said combustion chamber, said igniter comprising a housing having a mixing chamber therein and a discharge passageway communicating therewith, means for supplying combustible gas to said mixing chamber to be discharged through said passageway, a refractory metal cup in the main combustion chamber mounted on the end of said housing to cover the end of said discharge passage, said cup being free of openings in the upstream side thereof, a coiled resistance lament positioned within said cup and having one end grounded thereto, a source of electrical energy, a switch con- References Cited in the le of this patent UNITED STATES PATENTS Number Name Date v1,625,630 Scott Apr. 19, 1927 1,646,503 Steward Oct. 25, 1927 1,994,860 Matson Mar. 19, 1935 2,090,039 Goddard Augj17, 1937 2,117,108 Spencer May 10, 1938 2,385,699 Fox Sept. 25, 1945 2,402,763 Longini June 25, 1946 2,404,335v Whittle July'l, 1946 

